Add Clang 21 CI build

Author: offa

.github/workflows/ci.yml

@@ -14,8 +14,8 @@ jobs:
         compiler:
           - gcc:15
           - gcc:14
+          - clang:21
           - clang:20
-          - clang:19
     container:
       image: "registry.gitlab.com/offa/docker-images/${{ matrix.compiler }}"
     name: "${{ matrix.compiler }}"

.gitlab-ci.yml

@@ -8,7 +8,7 @@ build:
       - COMPILER: gcc
         VERSION: [15, 14]
       - COMPILER: clang
-        VERSION: [20, 19]
+        VERSION: [21, 20]
   image: registry.gitlab.com/offa/docker-images/${COMPILER}:${VERSION}
   script:
     - script/ci_setup.sh